Ethernet was originally defined in the early 1980s as a 10-Mbit/s shared-medium local area network (“LAN”), but has since been developed enormously and is now being deployed in access networks at speeds of up to 1 Gbit/s. Because Ethernet is so widely used, and virtually all networking starts and finishes through an Ethernet port on a personal computer (“PC”) somewhere, using Ethernet as an access technology is being adopted by access network Service Providers (“SPs”) in addition to asynchronous transfer mode (“ATM”) services.
The case for Ethernet and ATM in the access network is tied to demand for the sorts of services that need high bandwidth. For example, video-based applications are pushing at the bounds of what conventional digital subscriber line (“DSL”) services can deliver, forcing SPs to implement additional bandwidth-on-demand features into their DSL networks to support video-on-demand (“VOD”). Access standards such as International Telecommunication Union (“ITU”) Telecommunication Standardization Sector (“ITU-T”) G.998.1 (“ATM-Based Multi-Pair Bonding”), ITU-T G.998.2 (“Ethernet-Based Multi-Pair Bonding”), and Institute of Electrical and Electronics Engineers (“IEEE”) 802.3ah (“Media Access Control Parameters, Physical Layers, and Management of Parameters for Subscriber Access Networks”), which are incorporated herein by reference, provide a partial answer to bandwidth requirements of this type. Note that the acronym “xDSL” or “XDSL” is commonly used to denote any of the various types of DSL technologies.
Consider the case of Ethernet. The local loop (or pair or line) is the all-important link between the end user and the SP's network. On one end of the loop is the SP's equipment, the access node, which resides at a central office (“CO”) or point-of-presence (“POP”), acting as the gateway to the public network, directing data to and from the network core. On the other end of the loop is the subscriber. Currently, most subscribers connect to the SP's network using customer premises equipment (“CPE”) for one of several access technologies: PSTN/ISDN, XDSL, cable, T1/E1, T3/E3, OC3/STM1, and so on. The CPE in this case, however, acts not just as a bridge, but as a translation point between the access network and the local Ethernet network. This adds a further level of network deployment and maintenance complexity for both the SP and the subscriber. In contrast, with IEEE 802.3ah Ethernet access the subscriber connects his Ethernet LAN directly to the access network with a simple, familiar, and native Ethernet interface. IEEE 802.3ah allows Ethernet to be deployed over the existing copper loop by using, at a minimum, a single copper pair.
By bonding multiple copper pairs together, higher bandwidth services may be provided over longer distances. The ITU-T G.998.1, ITU-T G.988.2, and IEEE 802.3ah standards allow standard XDSL technology to run at higher speeds over multiple bonded pairs. The bonded approach treats multiple copper lines as a unified physical layer, making it far more robust than traditional inverse multiplexing (e.g., inverse multiplexing for ATM (“IMA”)) techniques. With respect to Ethernet, IEEE 802.3ah provides the ability to auto-detect which pairs are connected between two devices and are, therefore, eligible to be aggregated into a single Ethernet connection. Using this bonding auto-detection, SPs are not forced to configure the cross-connect information on each device. Instead, an IEEE 802.3ah-capable switch exchanges information to negotiate which pairs are connected to the same remote CPE system, and then creates an aggregate port from those pairs. Pairs can even come and go, being added and removed dynamically, without affecting the operational status of the aggregate port. In addition, IEEE 802.3ah provides an aggregation multiplexing and de-multiplexing layer into the Ethernet stack that is responsible for taking an Ethernet frame and partitioning it over multiple variable speed links in a manner that best utilizes the speed of each pair. For example, an implementation could partition a frame into variable size fragments, where the size of the fragments depends upon the speed of the link, with the faster links carrying the larger fragments.
Thus, using standards such as ITU-T G.998.1, ITU-T G.988.2, and IEEE 802.3ah a SP may use multiple DSL lines to carry a single ATM or Ethernet stream from a CO node to a CPE terminal in order to increase access bandwidth. This is advantageous as it is common for a subscriber's residence to have multiple twisted pairs available for connection to a CO, although only one pair is normally used. As such, logically bonding multiple pairs together can be used to increase access bandwidth to the subscriber's residence.
One problem with logically bonding multiple pairs together is that, in general, each pair has a different line rate and/or transmission characteristics due to, for example, differing noise levels, loading coils, lengths, etc. In addition, the line rate of each pair may be subject to multiple constraints that may be imposed by various standards, SPs, or the CPE system itself. This makes the manual splitting of a group rate among bonded pairs difficult and impractical when a large number of lines need to be configured by the SP. Therefore, effective automatic optimal allocation of bandwidth among the pairs is a critical aspect of any bonding implementation.
In particular, SPs typically have a large number of DSL subscribers that need to have their DSL service configured. The condition of DSL lines may be significantly different and multiple constraints may need to be met in the rate split. For example, subscribers may require that each of their lines meets a configured per-line minimum rate after the group rate split. As another example, standards typically specify a 4:1 line speed ratio, however, manual methods for rate splitting may not always guarantee this ratio. These constraints make manual rate splitting methods difficult, if not impossible, and hence an effective method for automatically splitting the group rate among bonded DSL lines is required.
However, while standards such as ITU-T G.998.1, ITU-T G.998.2, and IEEE 802.3ah may describe many aspects of the ATM-based and Ethernet-based bonding, they are silent with respect to the allocation of a group's bandwidth to lines within the group. In addition, techniques such as IMA for logically combining multiple physical links (e.g. DS1, E1, etc.) into one logical link require that all links must be of the same rate for synchronized framing. Hence, techniques such as IMA are not helpful as they do not require the allocation of a group bit rate among bonded lines.
A need therefore exists for an improved method and system for allocating a group bit rate among multiple logically bonded XDSL pairs in an ATM or Ethernet based communications network. Accordingly, a solution that addresses, at least in part, the above and other shortcomings is desired.